Instant Restore failed... Avamar / vCentre 8 / ESXi 8

Since moving from vCenter7 to vCenter8 we are having issues with IA. 

The NFS share is appearing on the host and the vm is registering, but we get the following errors in the Avamar logs: 

vmir Error <42570>: Query create VM failed to start with error: RuntimeFault.summary

vmir Error <0000>: Failed to create VM

This KB article (https://www.dell.com/support/kbdoc/en-uk/000213173/instant-acess-restore-fails-vmir-error-42570-query-create-vm-failed-to-start-with-error-runtimefault-summary) suggests its a setting on the ESXi host, but which one???? 

VMWare support have not got a clue.... and Dell support just say to talk to VMWare support.... going round in circles...  please help!

The host(s) we have tried are all in a cluster, i have tried hosts running ESXi v7.0.3 and ESXi v8.0, i have even enabled secure boot as people online reference vTPMs, but we are not using these?! 

Thanks in advance to anyone who can shed some light on this very frustrating issue!